ASUS started shipping the first motherboards with support for the USB 3.0 and 6Gbps SATA interfaces two months ago at the beginning of November. The first mobos were targeted at enthusiasts, but soon made their way into the mainstream. Gigabyte followed suit, and shipped seven new motherboards with support for the new interfaces as well.

At that time, ASUS told DailyTech that it was developing a PCIe adapter for all of its motherboard customers who wanted to upgrade to the new standards. The U3S6 card would plug into a PCIe x4 or x8 connector and add two USB 3.0 and two 6Gbps SATA ports to an ASUS system.

The company has now informed us that development and testing on the new U3S6 card has finished, and mass production has started. It will begin shipping to the channel next week, with e-tail availability expected for two weeks from now. Best of all, the U3S6 card will go on sale with a retail price of only $30.

Although ASUS has only officially validated the add-in card on their motherboards, there should be no problems encountered by customers wishing to use the adapter card on motherboards made by other brands, since the U3S6 complies fully with the PCIe specifications.

I think that this card is designed with the Asus P7P55D motherboards in mind.I don't remember well but the second 16x slot was not connected directly to the processor or something like that, and it could work as 4x without crippling the video card slot.

So it should be fine on asus motherboards. On other mobos you have to put it in a 16x slot and risk to get 8x/8x